In recent years, interest has grown in renewable source-based alternatives for organic functional materials that can serve as feedstocks for organic compound that have been made traditionally from petroleum or fossil-based hydrocarbons. As an abundant bio-based or renewable-resource, carbohydrates represent a viable alternative feedstock for producing such materials. Biomass contains carbohydrates or sugars (i.e., hexoses and pentoses) that can be converted into value added products from renewable hydrocarbon sources. Sugar alcohols, such as sorbitol, mannitol, iditol, arbitol or xylitol, are one kind of sugar-derived compounds that can be further transformed into various kinds of materials, which in turn can be further modified.
The molecule 1,2,5,6-hexanetetrol (“HTO”) is a by-product of the hydrogenolysis of sugar alcohols. Over the past century, various researchers have worked to prepare 1,2,5,6-HTO. For example, Zartman and Adkins reported in 1933 the synthesis of 1,2,5,6-hexanetetrol (1,2,5,6-HTO) by hydrogenolysis of sorbitol at 250° C. under 300 atm H2 using copper-chromium oxide catalyst. (Zartman W., Adkins H., J. Am. Chem. Soc., 55, 4559 (1933).) In 1958, Gorin and Perlin reported the hydrogenolysis of 1,2-O-isoprpylidene-d-glucofuranose in a stirred batch under H2 at 2000-2900 psi at 180° C. for 6 hrs in the presence of copper chromium oxide catalyst and the subsequent separation of 1,2,5,6-HTO by liquid-liquid extraction. (Gorin, P. A. J., Perlin, A. S., Canadian Journal of Chemistry (1958) v. 36, pp. 661-6.) In 1989, Urbas claimed the synthesis of “3,4-dideoxyhexitol” (1,2,5,6-hexanetetrol) via the catalytic hydrogenolysis of sorbitol, in a stirred batch reaction using 85% CuO and 15% Cr2O3 under 184-150 atm H2 at 200° C. for 3 hrs and the subsequent acid catalyzed dehydration of 1,2,5,6-HTO to 2,5-bis(hydroxymethy)tetrahydrofuran (U.S. Pat. No. 4,820,880). Montassier describes a heterogeneous catalysis of sorbitol by a retro-Michael reaction to selectively yield glycerol from sorbitol favored on certain copper-based catalysts. (Montassier, C., et. al., Bulletin de la Societe Chimique de France (1989) (2), 148-55.) Ludwig mentions 1,2,5,6-HTO as a nearly 4% wt by-product in the synthesis of diols from sucrose, in a batch reaction, using CoO, CuO, Mn3O4, H3PO4, and MoO3 at 160 C, under 280 bar H2, for three hours but does not claim any methods for purification of the 1,2,5,6-HTO (DE 3928285 A1). Cargill mentions it as an impurity in a patent for the purification of sorbitol hydrogenolysis reactions using sweep gas (International Patent Application No. WO08057263). In 1997, Maier reported selective catalytic synthesis of 1,2,5,6-HTO by double asymmetric dihydroxylation of 1,5-hexadiene in one step, with purification of the meso compound by liquid-liquid extraction. (Maier, M. E., Reuter, S., Liebigs Annalen/Recueil (1997) (10), 2043-2046.) Also, by direct oxidation of unsaturated hydrocarbons, Milnas reports the synthesis of 1,2,5,6-HTO with H2O2 in anhydrous tert-butanol in the presence of OsO4 (Milas, N. A., Sussman, S., J. Am. Chem. Soc., (1937) 59, 2345-7; U.S. Pat. No. 2,437,648).
1,2,5,6-HTO and other polyols having fewer oxygen atoms than carbon atoms may be considered a “reduced polyols.” Corma et al. disclose generally that higher molecular weight polyols containing at least four carbon atoms can be used to manufacture polyesters, alkyd resins, and polyurethanes. (Corma et al., “Chemical Routes for the Transformation of Biomass into Chemicals,” 107 Chem. Rev. 2443 (2007)). 1,2,5,6-HTO is mentioned, for example, as a starting material for the synthesis of diols (International Patent Application No. WO13163540) and for more esoteric multistep syntheses of small molecules (See, e.g., Machinaga, N., et al, Journal of Organic Chemistry, 1992, 57, 5178; Fitremann, J., et al, Tetrahedron, 1995, 51, 9581; Mayumi A., et al., Tetrahedron Letters (2000), 41(8), 1199-1203.).
As a useful intermediate in the formation of higher value chemicals, the industrial production of 1,2,5,6-HTO can be commercially important. For instance, 1,2,5,6-HTO is of primary commercial interest as a feedstock for the synthesis of adipic acid via continuous, selective oxidation. Adipic acid is used industrially to produce polyurethanes, plasticizers, lubricant components, polyester, and as food ingredient. Adipic acid's primary industrial outlet is in the production of Nylon-6,6 fibers and resins which, in 2010, accounted for 65% of the di-carboxylic acid's total 2.6 MM tons produced globally (See, e.g., Polen, T., et al., Journal of Biotechnology 167 (2013) 75-84).
Subsequent to the original work by Zartman et al. the literature is relatively sparse with references to 1,2,5,6-HTO compound, especially with regard to its production, isolation and purification. Given the recent increase in interest of using sugar-alcohols as a carbon resource and the value of 1,2,5,6-HTO as a potential commercial feedstock, various industrial and research entities are beginning to gather resources to develop better ways of making and separating this compound. Hence, a need exists for a method for isolating and purifying 1,2,5,6-HTO from a hydrogenolysis reaction mixture. In particular, a protocol that can be adapted to high-volume throughput systems would be welcome.